1. Field of the Invention
The present invention relates to a data relay device, a data relay method and a data transmission system using the device which is used for a data transmission system corresponding to a high-definition multimedia interface (HDMI) using, for example, high-bandwidth digital content protection (HDCP) and relays to output a data output from content [audio video (AV) data, etc.] transmitting equipment to content receiving equipment.
2. Description of the Related Art
In recent years, the HDMI for a next-generation television has been standardized. This HDMI is a digital interface standard for the next-generation television with a function for a household electrical appliance added thereto while holding low order interchangeability on the basis of a digital video interface (DVI) which has been frequently adopted to a PC display device, etc., and transfers high-definition (HD) video and multi-channel audio through a signal connector to have an advantage for routing wires compared to the DVI. The HDMI is also compatible with the HDCP for a digital image signal.
By the way, an AV data relay device sometime interposes between AV data transmitting equipment and AV data receiving equipment (for example, a case of interposition of an AV amplifier between a DVD reproduction device and a monitor device). In this system configuration, up to now, in the case of the presence of difference in specifications between the AV data receiving equipment and the data relay device, since control data indicating a specification content of the receiving equipment is informed to the transmitting equipment via the relay device, the transmitting equipment transmits data in accordance with the specification of the receiving equipment, then, this system can not take advantage of specification of the relay device.
For example, since the specification of the receiving equipment takes priority if the receiving equipment has the specification of audio 2-channel and the relay device has the specification of audio 5.1-channel, the relay device receives the data of the audio 2-channel from the transmitting equipment and cannot take advantage of the audio 5.1-channel.
An example of the data transmission system employing the above-mentioned HDCP is disclosed in, for example, Jpn. Pat. Appln. KOKAI 2004-015104. The system disclosed in this document allows the relay device to select a set of transmitting equipment in the case of sharing the plurality of sets of transmitting equipment with a single set of receiving equipment. And the system doest take account of the problem in the case that there is a difference in specification between the relay device and the receiving equipment.
As mentioned above, up to this time, in the system configuration in which the data relay device is interposed between the data transmitting equipment and the data receiving equipment, when the specifications differ between the data receiving equipment and the data relay device, the control data indicating the specification content of the receiving equipment is notified to the transmission equipment through the relay device, so that there is the problem that the transmitting equipment transmits data in accordance with the specification of the receiving equipment and the system configuration can not take advantage of the specification of the relay device.